On Thu, May 28, 2015 at 06:09:34PM +0100, Michel Thierry wrote:
> And prevent overflow warning during compilation. We already set this limit
> for the GGTT.
>
> This is a temporary patch until a full replacement of size_t variables
> (inadequate in 32-bit kernel) is in place.
>
> Regression from:
> commit a4e0bedca678c81eea4cd79a4bd502335639f73a
> Author: Michel Thierry <michel.thierry@xxxxxxxxx>
> Date: Wed Apr 8 12:13:35 2015 +0100
>
> drm/i915: Use complete address space in true PPGTT
>
> v2: Prettify code and explain why this is needed. (Chris)
>
> Suggested-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Michel Thierry <michel.thierry@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem_gtt.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 17b7df0..0653c28 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -951,7 +951,16 @@ static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
> gen8_initialize_pd(&ppgtt->base, ppgtt->scratch_pd);
>
> ppgtt->base.start = 0;
> - ppgtt->base.total = 1ULL << 32;
> +#ifdef CONFIG_X86_32
FWIW, this is somewhat frowned upon (which is why Chris was using
IS_ENABLED(). It's documented in Documentation/CodingStyle, Chapter 20.
Within code, where possible, use the IS_ENABLED macro to convert a Kconfig
symbol into a C boolean expression, and use it in a normal C conditional:
if (IS_ENABLED(CONFIG_SOMETHING)) {
...
}
The compiler will constant-fold the conditional away, and include or exclude
the block of code just as with an #ifdef, so this will not add any runtime
overhead. However, this approach still allows the C compiler to see the code
inside the block, and check it for correctness (syntax, types, symbol
references, etc). Thus, you still have to use an #ifdef if the code inside the
block references symbols that will not exist if the condition is not met.
--
Damien
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